Here, we describe the case of a 74-year-old male patient with a high-risk prostate carcinoma who underwent positron-emission tomography/computed tomography (PET/CT) with [ ⁶⁸ Ga]Ga-prostate-specific membrane antigen ([ ⁶⁸ Ga]Ga-PSMA-11) for staging. [ ⁶⁸ Ga]Ga-PSMA-11 PET/CT detected an extensive area of increased tracer uptake at the prostatic level, involving both lobes. Additionally, a rounded lesion approximately 4 cm in diameter was identified in the celiac region adjacent to the stomach, exhibiting moderate tracer uptake. Based on these imaging findings, the patient underwent radiation therapy applied to the prostate and pelvis and a biopsy of the suspected lesion adjacent to the stomach, which was positive for Siewert type III gastroesophageal junction adenocarcinoma (HER2-negative, PDL-1 60%). This case demonstrates the importance of not overlooking incidental tracer uptakes in PSMA PET/CT imaging in the stomach, as they could represent neoplastic lesions.